Houghton Mifflin has put all of the major Tolkien works on sale today (Kindle e-books) for $2.99 each, if you are looking to fill any holes. From The Hobbit through Fall of Gondolin, pretty much everything I checked was on sale. This is a "deal of the day" so prices will go back up at the end of today.

Looks like a lot of people took advantage! Here is the top ten list of titles purchased (through the link I shared), which I thought was interesting. I know I used the sale to fill a few holes (mostly for searchable text which is often quite handy).

1 The Fall of Gondolin2 Beren and Lúthien3 The Lord of the Rings: One Volume4 Unfinished Tales of Numenor and Middle-earth5 The Children of Húrin6 The Silmarillion7 Beowulf: A Translation and Commentary8 The Story of Kullervo9 The Lay of Aotrou and Itroun10 The Book of Lost Tales, Part One (History of Middle-Earth 1)

I agree! I think (just supposition on my own here) that with the pipeline of material slowing down from Christopher, that they are going back and filling in some holes. The e-book market is definitely more viable now than it was 10-20 years ago to cover the investment.